The invention relates to a process and a device for the rotation-angle-monitored tightening or loosening of screw connections of the type generally described in German patent document DE 32 21 658 A1.
German patent document DE 32 21 658 A1 relates to a torque spanner having an associated plug-in insert--hereinafter referred to as a socket or socket--for a threaded screw nut, to be screw or threadably connected, for the partial checking of screw connections, in which torque spanner the attainment of the yield point of a screw connection is ascertained and indicated by torque measurements. The torque spanner exhibits a torque meter for measuring the exerted torque, an angle transmitter for measuring the rotation of the torque spanner in relation to a fixed reference point and an analyzing and indicating device for the determined values. For the measurement of the rotation angle, an enclosure housing, concentrically surrounding the socket, is applied fixedly to the workpiece, which is disposed pivotably about the swivel axis of the torque spanner, which swivel axis is aligned parallel to the screwdriver shaft of the torque spanner. This securement of this one enclosure housing predefining, with respect to the rotation angle, a fixed spatial point is effected by means of a rigid axle and a fastening unit disposed on the rigid axle, e.g. a magnet or a further socket secured to an adjacent screw nut. For devices which are designed for the tightening of a large number of differently disposed screws, this securement is not suitable however, since the configuration of the rigid axle and the fastening unit have to be matched for each type of screw connection. Furthermore, the rigid axle, in particular, exhibits a spatial extent which makes handling of this type of device more difficult or which, partly for space reasons, prevents it from being used.
From German patent document DE 31 27 753 A1, a hand-guided, power-operated screwdriver or torque spanner is known, such as is used, for example, for the assembly of motor vehicles. The power-operated screwdriver is provided, for the recording of a torque/rotation-angle diagram, with a torque-measuring device and with a rotation-angle-measuring device, the torque/rotation-angle diagram serving to monitor a realized screw connection. The torque-measuring device is designed to measure the torque delivered to the screwdriver shaft . The rotation-angle-measuring device is designed to record the rotation angle covered by the screwdriver shaft, the housing of the power-operated screwdriver being used as the reference for the rotation angle of the screwdriver shaft. In the case of handguided power-operated screwdrivers, which have to forgo a support securing their position in space, the operator of the power-operated screwdriver reacts variably to a developing torque, as a result of which this motion is superimposed upon the rotation angle of the screwdriver shaft. This fact is particularly disadvantageous in the end-tightening which is important for the evaluation of the screw connection, since here the housing is very often deflected or deviates to a considerable degree, thereby making the values determined in this period extremely unreliable.
An object of the invention is to further improve the tools of the above-described general types while maintaining their advantages and facilities, namely an accurate and absolute recording of the rotation angle of the screw or nut to be tightened and a process monitoring for all known screwing methods, by providing further advantages of
(i) a simple design, PA1 (ii) comfortable and fast tool maneuverability; and PA1 (iii) universal applicability, irrespective of the local conditions in the environment of the screw or other threaded connection location. PA1 determining a first angle corresponding to the rotation angle of the drive part with respect to the housing, PA1 determining a second angle corresponding to the rotation angle of the housing with respect to a fixed point, and PA1 determining an absolute rotation angle of the drive pare with respect to the fixed point by combining the first and second angles.
This object is achieved according to the preferred embodiments of the invention by a system which is capable of:
As a result of the determination of the absolute rotation angle in certain preferred embodiments with respect to the screwdriver or tool shaft aligned parallel to the screw-in axis of the screw connection, with the aid of an inertial rotation-rate sensor, which is assigned to the housing and/or to the screwdriver shaft parallel to the swivel axis and which replaces the fixed spatial point of the generic type by a spatially fixed virtual fixed point, in the case of the rotation-angle-monitored screwing-in tool, hereinafter referred to as a screwdriver such as, for example, a torque spanner or power-operated screwdriver, a simple construction, comfortable and fast maneuverability and universal usability are achieved.
Older power-operated screwdrivers which are driven by drive shafts and are rotation-angle-monitored by increment transmitters, for example, can also be easily retrofitted with the same rotation-rate sensor for good rotation-angle determination. This can be effected by the fact that, using the rotation-rate sensor, a deflection of the housing about the screwdriver shaft and hence about the screw-in axis of the screw connection is determined and is added, in a manner producing a correct digit-sign (rotational direction sign), to the number of rotations, determined by means of the increment transmitter, of the drive and/or screwdriver shaft, thereby enabling the correction of a rotation angle which has been erroneously determined in the event of the housing having been deflected about the screwdriver shaft.